Specific Aims The specific aims of the Data Collection Project are to: [unreadable] Trace and locate respondents who participated in Wave I of Add Health with a goal of locating 92% of our respondents for re-interview in Wave IV. [unreadable] Develop and pilot a 90-minute CAPI/CASI survey instrument to be administered on a laptop computer, protocols for collecting physical measurements and biological specimens, and procedures to record and geocode spatial data obtained at the interview. [unreadable] Conduct a Wave IV two-hour personal interview with original Wave I Add Health respondents during which the following data are collected: survey data reflecting both longitudinal and new information, longitudinal anthropometric data, biological data from blood spots and a blood pressure monitor, genetic data from DNA, and geographic locations for longitudinal spatial data. Our goal is an 85% reinterview rate. [unreadable] Serve as the core data resource for this program project continuation, providing data for program and Satellite Investigators to carry out their proposed research, and for the entire scientific community of current and future Add Health public users.